Light emitting device, electronic appliance, and method for manufacturing light emitting device

ABSTRACT

To provide a light emitting device that has a structure in which a light emitting element is sandwiched by two substrates to prevent moisture from penetrating into the light emitting element, and a method for manufacturing thereof. In addition, a gap between the two substrates can be controlled precisely. In the light emitting device according to the present invention, an airtight space surrounded by a sealing material with a closed pattern is kept under reduced pressure by attaching the pair of substrates under reduced pressure. A columnar or wall-shaped structure is formed between light emitting regions inside of the sealing material, in a region overlapping with the sealing material, or in a region outside of the sealing material so that the gap between the pair of substrates can be maintained precisely.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/869,903, filed Aug. 27, 2010, now allowed, which is a divisional ofU.S. application Ser. No. 11/017,888, filed Dec. 22, 2004, now U.S. Pat.No. 7,792,489, which claims the benefit of a foreign priorityapplication filed in Japan as Serial No. 2003-433025 on Dec. 26, 2003,all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light emitting elementcomprising an anode, a cathode, and a layer containing an organiccompound that emits light by being applied with an electric field(hereinafter, referred to as an electroluminescent layer), and a lightemitting device using the same. In particular, the invention relates toan electronic appliance mounted with a light emitting display device,which comprises a TFT and an organic light emitting element, as acomponent part.

In the present specification, a light emitting device indicates an imagedisplay device, a light emitting device, a light source (including alighting device), and the like. The light emitting device furtherincludes all of a module in which a light emitting device is attachedwith a connector, e.g., an FPC (flexible printed circuit), a TAB (tapeautomated bonding) tape, or a TCP (tape carrier package); a modulehaving a printed wiring board provided on an end of a TAB tape or a TCP;and a module in that a light emitting element is directly mounted withan IC (integrated circuit) by the COG (chip on glass) technique.

2. Description of the Related Art

In recent years, a research related to a light emitting device having anEL element as a self-luminous light emitting element has been activated.Such a light emitting device is also referred to as an organic ELdisplay or an organic light emitting diode. The light emitting devicehas advantages of being high-speed response that is suitable fordisplaying moving images, low voltage, low power consumption drive, andthe like. Therefore, the light emitting device has been attractingattention as a next generation display device such as a new generationcellular phone and personal digital assistance (PDA).

An EL material for forming an EL layer is very easily deteriorated. Inparticular, the EL material is easily deteriorated due to existence ofoxygen or moisture, and therefore, the EL material had drawbacks inwhich luminance of a light emitting element is lowered and life thereofis shortened.

Conventionally, moisture etc. has been prevented from penetrating into alight emitting element as follows: the light emitting element is coveredwith a sealing can while an inert gas is filled in the interior of thesealing can and a drying agent is pasted therein.

The present applicant discloses a structure in which a pair ofsubstrates is attached to each other with a sealing material and aportion surrounded by the sealing material is filled with a resin toencapsulate a light emitting element in patent document 1.

The present applicant further discloses a structure in which a pair ofsubstrates is attached to each other by using a filler to encapsulate alight emitting element in patent document 2.

The present applicant still further discloses a light emitting elementin which a columnar spacer is provide between a pair of substrates inpatent document 3.

-   [Patent Document 1]: Japanese Patent Application Laid-Open No.    2001-203076-   [Patent Document 2]: Japanese Patent Application Laid-Open No.    2001-93661-   [Patent Document 3]: Japanese Patent Application Laid-Open No.    2000-196438

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light emittingdevice with a structure in which a light emitting element is sandwichedby two substrates to prevent moisture from penetrating into the lightemitting element, and a method for manufacturing the same. It is anotherobject of the invention to control a gap between the two substratesprecisely.

In the invention, a substrate with a light emitting element formedthereon and a transparent sealing substrate are attached to each otherunder reduced pressure, columnar or wall-shaped structures are providedon one of or both the substrates to maintain a gap between thesubstrates.

The invention provides a light emitting device in which a pair ofsubstrates is attached to each other under reduced pressure so that asealed space surrounded by a sealing material with a closed pattern iskept under negative pressure. By keeping the sealed space under negativepressure purposely, the pair of substrates can be attached to each othermore tightly. Since the sealed space is kept under negative pressure,the both substrates might be curved by being applied with pressure sothat a gap between the substrates might be narrowed in the vicinity ofthe center of a pixel portion. When columnar or wall-shaped structuresare provided in the pixel portion, however, the pressure applying to thesubstrates is dispersed, thereby preventing bending and cracking of thesubstrates. In particular, when large-size substrates are attached toeach other, they are easily curved. In the case where light emitted froma light emitting element passes through the curved substrates, the angleof refraction is varied with location. According to the invention,however, bending of the substrates can be prevented by providing thecolumnar or wall-shaped structures, which permits favorable display.

Conventionally, since a sealing substrate has been attached to asubstrate with a light emitting element formed thereon under atmosphericpressure, a sealed space surrounded by a sealing material has been keptunder positive pressure. Therefore, the sealing material has been partlypushed out to be broken due to the pressure difference between thepositive pressure and the atmospheric pressure. Since the positivepressure within the sealed space has been kept after the sealing step,the adhesiveness between the substrates has been reduced. When thesealed space has been kept under positive pressure, the both substrateshave been curved mutually so that a gap between the substrates has beenwidened in the vicinity of the center of a pixel portion. In the casewhere the sealed space is formed to have a protruded shape like asealing substrate that is partly cut by processing or a sealing can,since the sealed space has a large volume, the above-mentioned problemsdue to the pressure difference has not been not caused prominently.

In the invention, the columnar or wall-shaped structures are preferablyprovided in a portion where does not overlap with a light emittingregion and elements such as a TFT. For example, the columnar orwall-shaped structures can be provided between light emitting regionsinside of a sealing material, in a region overlapping with the sealingmaterial, or in a region outside of the sealing material. Thearrangement of the columnar or wall-shaped structures overlapping withthe sealing material can improve the adhesiveness between the substratesand maintain a gap therebetween.

The sealing material may contain a gap material for maintaining a gapbetween the substrates (such as a filler (e.g., a fiber rod), and a fineparticle (e.g., a silica spacer)). A pixel portion in which multiplelight emitting elements are disposed, a driver circuit, and theperiphery thereof on the substrate are surrounded with the sealingmaterial. The sealing material is formed to have a closed pattern suchas a square shape.

According to providing columnar or wall-shaped structures in a regionoutside of the sealing material, in the case where a plurality of pixelportions are formed on one substrate (so-called multiple pattern),pressure can be dispersed not only attaching substrates under reducedpressure but also dividing a pair of substrates into respective panels.

It is still another object of the invention to improve light extractionefficiency of light emitting elements by reducing a volume of the sealedspace, narrowing a gap between substrates, and maintaining the gaptherebetween. It is preferable that the sealed space be filled with afiller in which a difference in refractive index between the filler andthe substrates is 0 or more and 0.7 or less, rather than an inert gashaving a controlled dew point. When using a glass substrate with arefractive index of about 1.55, for example, a UV curing epoxy resin(#2500 Clear manufactured by Electro-Lite Corporation) having therefractive index of 1.50 may be used as the filler. The whole lighttransmittance can be increased by filling the filler with the refractiveindex that is different of those of the substrates in the range of 0 to0.7 between the pair of substrates.

Meanwhile, in the case of a liquid crystal display device, there is amethod for filling a liquid crystal between a pair of substrates underreduced pressure. In the method, since the liquid crystal exists in aspace surrounded by the pair of substrates and a sealing material, andtherefore, the liquid crystal display device does not have an airtightspace where is not filled with the liquid crystal. In the liquid crystaldisplay device, bending of the substrates is prevented to some extent byfilling the liquid crystal therebetween. On the other hand, in a lightemitting device, when a pair of substrates is attached to each otherunder reduced pressure, since a sealed space surrounded by the pair ofsubstrates and a sealing material is kept under negative pressure, thepair of substrates is easily dent seriously. This results in seriousfluctuation of the display. Therefore, when attaching the pair ofsubstrates for the light emitting device, certain conditions has beenrequired such that the sealed space is kept under almost atmosphericpressure or slight negative pressure.

When the filler is filled in a region surrounded by the sealingmaterial, it is preferable that the filler be dropped inside the regionsurrounded by the sealing material, and two substrates be attached toeach other under reduced pressure. When attaching the two substrates toeach other under reduced pressure, the columnar or wall-shapedstructures play an important role of maintaining a gap between thesubstrates precisely and dispersing pressure applied to the substratesso as to prevent cracking of the substrates.

Conventionally, since the substrates have been attached to each otherunder atmospheric pressure, it has been difficult to fill the filler inthe region surrounded by the sealing material, which results in defectsof mixing air bubbles therein or spilling the filler out of the regionsurrounded by the sealing material.

Since the filler filled in the space surrounded by the sealing materialis cured in the light emitting device, it also serves as a spacer sothat the cured filler can disperse pressure applied to the substratesefficiently to prevent cracking of the substrates.

The columnar or wall-shaped structures can be formed by patterning thefollowing materials into a predetermined pattern: an inorganic material(e.g., silicon oxide, silicon nitride, and silicon oxynitride); aphotosensitive or nonphotosensitive organic material (e.g., polyimide,acrylic, polyamide, polyimide amide, resist, and benzocyclobutene); aSOG film obtained by application (such as an SiOx film containing alkylgroup); or a lamination layer thereof. Also, the columnar or wall-shapedstructures can be made from either a negative photosensitive organicmaterial that is insoluble in etchant by light irradiation or a positivephotosensitive organic material that is soluble in etchant by lightirradiation.

Columnar or wall-shaped structures may contain a hygroscopic substance(e.g., calcium oxide, barium oxide, and the like) to function as adrying agent. The columnar or wall-shaped structures are orderly alignedin the pixel region, and therefore, they also serve as a drying agentthat is aligned efficiently. Conventionally, since a treatment forpasting a drying agent has been complicated, when a large-size substrateis used for mass-production, a large-scale device for attaching a dryingagent has been required.

In the case where a transparent electrode is used as an anode or acathode of a light emitting element and a pair of substrates is madefrom a material having light transmitting properties, a light emittingdisplay device that can display images on both a front surface and aback surface (hereinafter referred to as a dual emission type displaydevice) can be provided. When forming the dual-emission type displaydevice, it is preferable that columnar or wall-shaped structures and afiller be made from materials with light transmitting properties.Preferably, polarizing plates or circular polarizing plates are attachedon the both surfaces through which light is emitted so as to improve thecontrast.

According to one aspect of the invention, there is provided a lightemitting device including a pixel portion with a plurality of lightemitting elements, wherein each of the plurality of light emittingelements has a cathode, a layer containing an organic compound, and ananode between a pair of substrates, the pixel portion is provided overone of the pair of substrates, a columnar or wall-shaped structure isformed over at least one of the pair of substrates to maintain a gapbetween the pair of substrates, the pair of substrates is attached toeach other by a sealing material with a closed pattern, and an airtightspace surrounded by the pair of substrates and the sealing material iskept under reduced pressure.

According to another aspect of the invention, there is provided a lightemitting display device including a pixel portion with a plurality oflight emitting elements, wherein each of the plurality of light emittingelements has a cathode, a layer containing an organic compound, and ananode between a pair of substrates, the pixel portion is formed over oneof the pair of substrates, a columnar or a wall-shaped structure isformed over at least one of the pair of substrates to maintain a gapbetween the pair of substrates, the pair of substrates is attached toeach other by a sealing material with a closed pattern that surroundsthe pixel portion, a region surrounded by the sealing material is filledwith a filler, and difference in a refractive index between the pair ofsubstrates in contact with the filler and the filler is 0 or more and0.7 or less.

In the above aspects, the columnar or wall-shaped structure is disposedinside the sealing material, in a position overlapping with the sealingmaterial, or in a region outside the sealing material.

The columnar or wall-shaped structure contains a hygroscopic substance.

The cathode and anode for each of the plurality of light emittingelements are conductive films with light transmitting properties, andformed of indium tin oxide alloy (ITO), indium oxide zinc oxide alloy(In₂O₃—ZnO), zinc oxide (ZnO), or indium tin oxide containing SiOx(ITSO).

A first polarizing plate is provided on one of the pair of substrateswhereas a second polarizing plate is provided on another substrate. Byproviding the polarizing plates or circular polarizing plates, pureblack display can be performed during non-light emitting state, therebyincreasing the contrast.

The anode or cathode of each of the plurality of light emitting elementsis electrically connected to a TFT.

According to still another aspect of the invention, there is provided amethod for manufacturing a light emitting device that includes a pixelportion having a plurality of light emitting elements, wherein each ofthe plurality of light emitting elements includes a cathode, a layercontaining an organic compound, and an anode between a pair oftransparent substrates. The method further includes the steps of:forming the pixel portion over one of the pair of substrates; forming acolumnar or wall-shaped structure over at least one of the pair ofsubstrates; forming a sealing material with a closed pattern over atleast one of the pair of substrates; and attaching the pair ofsubstrates to each other under reduced pressure so that the sealingmaterial is disposed to surround the pixel portion.

According to yet another aspect of the invention, there is provided amethod for manufacturing a light emitting device that includes a pixelportion having a plurality of light emitting elements, wherein each ofthe plurality of light emitting elements includes a cathode, a layercontaining an organic compound, and an anode between a pair oftransparent substrates. The method further includes the steps of:forming the pixel portion over one of the pair of substrates; forming acolumnar or wall-shaped structure over at least one of the pair ofsubstrates; forming a sealing material with a closed pattern over atleast one of the pair of substrates; dropping a filler inside a regionsurrounded by the sealing material; and attaching the pair of substratesunder reduced pressure so that the sealing material is disposed tosurround the pixel portion, wherein the region surrounded by the sealingmaterial is filled with the filler.

In the light emitting device of the invention, the method for drivingscreen display is not particularly limited. For example, a dotsequential driving method, a line sequential driving method, a surfacesequential driving method, and the like may be used. The line sequentialdriving method is typically used, and a time division gray scale drivingmethod or a surface area gray scale driving method may also be employedarbitrarily. Further, a source line of the light emitting display devicemay be input with either analog signals or digital signals. A drivercircuit and the like may be designed arbitrarily according to the imagesignals.

Light emitting display devices using digital video signals areclassified into one in which video signals are input to a pixel at aconstant voltage (CV), and another one in which video signals are inputto a pixel at a constant current (CC). The light emitting devices inwhich video signals are input to a pixel at a constant voltage (CV) arefurther classified into one in which a constant voltage is applied to alight emitting element (CVCV), and another one in which a constantcurrent is supplied to a light emitting element (CVCC). The lightemitting devices in which video signals are input to a pixel at aconstant current (CC) is still classified into one in which a constantvoltage is applied to a light emitting element (CCCV), and another onein which a constant current is supplied to a light emitting element(CCCC).

A protection circuit (e.g., a protection diode) may be provided in thelight emitting device of the invention to inhibit electrostaticdischarge damage.

The present invention can be applied regardless of a TFT structure. Forexample, a top-gate TFT, a bottom-gate (inverted-stagger type) TFT,staggered TFT, and the like can be employed. The invention is notparticularly limited to a TFT with a single-gate structure, andtherefore, a TFT with a multi-gate structure having multiple channelformation regions, e.g., a TFT with a double gate structure may be used.

A light emitting element may be electrically connected to either ap-channel TFT or an n-channel TFT. When a light emitting element iselectrically connected to the p-channel TFT, the light emitting elementmay be formed as follows. A hole injecting layer, a hole transportinglayer, a light emitting layer, and an electron transporting layer aresequentially laminated on an anode, and a cathode may be formed on theelectron transporting layer. When a light emitting element iselectrically connected to the n-channel TFT, the light emitting elementmay be formed as follows. An electron transporting layer, a lightemitting layer, a hole transporting layer, and a hole injecting layerare sequentially laminated on a cathode, and an anode is formed on thehole injecting layer.

As an active layer of the TFT, an amorphous semiconductor film, asemiconductor film having a crystal structure, a compound semiconductorfilm having an amorphous structure, and the like may be usedarbitrarily. As the active layer of the TFT, a semiamorphoussemiconductor film (also referred to as a microcrystalline semiconductorfilm) can also be used. The semiamorphous semiconductor film has anintermediate structure between an amorphous structure and a crystalstructure (also including a single crystal structure and a polycrystalstructure), and a third condition that is stable in term of free energy,and further includes a crystalline region having a short range orderalong with lattice distortion.

Crystal grains with a size of 0.5 to 20 nm are contained in at least apart of the semiamorphous semiconductor film. Raman spectrum is shiftedtoward lower wavenumbers than 520 cm⁻¹. The diffraction peaks of (111)and (220), which are believed to be derived from Si crystal lattice, areobserved in the semiamorphous semiconductor film by X-ray diffraction.The semiamorphous semiconductor film contains hydrogen or halogen of atleast 1 atom % or more as a neutralizing agent for dangling bonds. Thesemiamorphous semiconductor film is formed by glow dischargedecomposition with silicide gas (plasma CVD). As for the silicide gas,SiH₄, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄ and the like can be used. Thesilicide gas may also be diluted with H₂, or a mixture of H₂ and one ormore of rare gas elements selected from He, Ar, Kr, and Ne. The dilutionratio is set to be in the range of 1:2 to 1:1,000. The pressure is setto be approximately in the range of 0.1 to 133 Pa. The power frequencyis set to be 1 to 120 MHz, preferably, 13 to 60 MHz. The substrateheating temperature may be set to be 300° C. or less, preferably, 100 to250° C. With respect to impurity elements contained in the film, eachconcentration of impurities for atmospheric constituents such as oxygen,nitrogen, and carbon is preferably set to be 1×10²⁰ cm⁻¹ or less. Inparticular, the oxygen concentration is set to be 5×10¹⁹/cm³ or less,preferably, 1×10¹⁹/cm³ or less. The electron field-effect mobility μ ofthe TFT using the semiamorphous semiconductor film as its active layeris 5 to 50 cm²/Vsec.

Further, the light emitting element (EL element) includes a layercontaining an organic compound that generates electroluminescence bybeing applied with an electric field (hereinafter referred to as an ELlayer), an anode, and a cathode. As electroluminescence generated in theorganic compound, there are luminescence (fluorescence) upon returningto a ground state from an excited singlet state, and luminescence(phosphorescence) upon returning to a ground state from an excitedtriplet state. The light emitting display device manufactured accordingto the invention can be applicable in the case of using eitherfluorescence or phosphorescence.

The light emitting element (EL element) having an EL layer includes astructure in which the EL layer is sandwiched between a pair ofelectrodes. The EL layer usually includes a lamination structure.Typically, the EL layer is formed by laminating “a hole transportinglayer, a light emitting layer, and an electron transporting layer”.

The EL layer may also includes a lamination structure as follows: a holeinjecting layer, a hole transporting layer, a light emitting layer, andan electron transporting layer are laminated on an anode; or a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting layer arelaminated on an anode. A light emitting layer may be doped with afluorescent pigment and the like. All of the above-mentioned layers maybe made from low molecular weight materials or high molecular weightmaterials. A layer containing an inorganic material (such as silicon)may be used. Note that layers sandwiched between an anode and a cathodeare collectively referred to as the EL layer throughout the presentspecification. The EL layer includes all of the above hole injectinglayer, the hole transporting layer, the light emitting layer, theelectron transporting layer, and the electron injecting layer.

According to the invention, when a pair of attached large-sizesubstrates is divided into multiple panels for mass-production, a lightemitting element is sandwiched by the two substrates while maintaining aconstant gap between the substrates, so that ingress of moisture intothe light emitting element can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1F are cross sectional views showing manufacturing stepsaccording to the invention (Embodiment Mode 1);

FIG. 2 is a top view showing a structure according to the invention(Embodiment Mode 1);

FIG. 3 is a top view showing a structure according to the invention(Embodiment Mode 1);

FIG. 4 is a top view showing a structure according to the invention(Embodiment Mode 1);

FIG. 5 is a cross sectional view according to the invention (EmbodimentMode 2);

FIG. 6 is a part of a top view showing a manufacturing device(Embodiment Mode 2);

FIG. 7 is an overall view showing a manufacturing device (EmbodimentMode 2);

FIG. 8 is a top view showing a manufacturing device (Embodiment 1);

FIGS. 9A and 9B are top views showing arrangements of spacers;

FIGS. 10A to 10D are diagrams showing electronic appliances mounted withlight emitting devices according to the invention; and

FIGS. 11A to 11C are diagrams showing electronic appliances mounted withlight emitting devices according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes of the invention will hereinafter be described.

Embodiment Mode 1

The present embodiment mode will explains a method for manufacturing alight emitting device in the case of the multiple pattern in which apair of attached substrates is divided into multiple patterns (e.g., twopieces of panels are manufactured from a pair of attached substrates)with reference to FIGS. 1A to 1F.

A second substrate 20 that will serve as a sealing substrate isprepared. Columnar spaces 15 are formed on the second substrate 20 (FIG.1A). The columnar spacers 15 are formed by patterning a level film inpredetermined portions. The height of the columnar spacers 15 isimportant, and determines a gap between two substrates. Although thecolumnar spacers are exemplified as structures for maintaining the gaptherebetween, the spacers may have a wall-shaped structure or agrid-like structure, or a combination of such shapes.

The columnar spacers may contain a drying agent.

Patterns of a sealing material 12 is formed by using a dispenser device,a droplet discharging device (e.g., an ink jet device), and the like(FIG. 1B). The sealing material 12 may be added with a filler formaintaining the gap between the substrates. The sealing material 12 isformed to have a closed pattern such that a pixel portion with lightemitting elements formed over a first substrate is surrounded by thesealing material when attaching the first and second substrates to eachother.

A filler 14 is dropped in a portion surrounded with the sealing materialby using the dispenser device, the droplet discharging device (the inkjet device), and the like. In the embodiment mode, the filler 14 havinglower viscosity than that of the sealing material 12 is dropped from adispenser 18 under an inert atmosphere (FIG. 1C). The dropping amount isdetermined by calculating the volume of a sealed space (i.e., a spacesurrounded by the pair of substrates and the sealing material) inadvance so as to drop the appropriate amount of the filler.

Subsequently, the second substrate 20 and a first substrate 10 with thelight emitting elements formed thereon are attached to each other underreduced pressure (FIG. 1D). Since the light emitting elements aresensitive to moisture, the substrates are preferably attached to eachother in an atmosphere with a dew point as low as possible.

In the first substrate 10, a TFT 13 is formed on a base insulating film11 and an anode 17 of a light emitting element is connected to one ofelectrodes for the TFT 13. Ends of the anode 17 are covered with apartition wall 16 that is made from an insulating material. A layer 30containing an organic compound is provided to be in contact with theanode 17. A cathode 21 is formed so as to cover the partition wall 16and the layer 30 containing the organic compound. The light emittingelement includes the anode 17, the layer 20 containing the organiccompound, and the cathode 21 to form a light emitting region. The secondsubstrate 20 is preferably attached to the first substrate 10 such thatthe columnar spacers 15 are not overlapped with the light emittingregion and the TFT 13.

FIG. 2 is a top view showing an example of pixels upon attaching thepair of substrates. As shown in FIG. 2, it is preferable that thecolumnar spacers 15 be disposed such that they do not overlap with lightemitting regions 24R, 24G, 24B, and element portions (including the TFT13) 23, respectively. Note that portions identical to those in FIGS. 1Ato 1F are denoted by same reference numerals in FIG. 2.

FIG. 3 shows an example in which a wall-shaped spacer 35 is provided assubstitute for the columnar spacers. As shown in FIG. 3, the wall-shapedspacer 35 is disposed so as not to overlap light emitting regions 34R,34G, 34B, and element portions (including TFTs) 33.

FIG. 4 shows an example in which a grid-like spacer 45 is provided inplace of the columnar spacers. As shown in FIG. 4, the grid-like spacer45 is disposed such that it does not overlap with light emitting regions44R, 44G, and 44B while it partly overlaps with element portions(including TFTs) 43. In the case of forming the grid-like spacer 45,since it occupies a larger area as compared with the columnar andwall-shaped spacers, if pressure is applied to the pair of substrates,the pressure is dispersed. Therefore, the grid-like spacer may overlapthe element portions partly. In this case, the light emitting regions44R, 44G, 44B are partitioned by the grid-like spacer 45, respectivelyso that the light emitting elements are sealed more firmly. That is, aplurality of airtight spaces is further formed inside the sealed spacesurrounded by the sealing material.

When the second substrate 20 is attached to the first substrate 10 withthe light emitting elements formed thereon, the partition wall (alsoreferred to as a bank) 16 also serves as a structure for maintaining thegap between the substrates.

Note that although only one pixel is illustrated in FIGS. 1A to 1F forthe sake of simplification, in fact, multiple pixels (n rows×m columns)are arranged.

Next, the sealing material 12 or the filler 19 is cured by heattreatment or irradiation with light so that the pair of attachedsubstrates is fixed to each other (FIG. 1E). Thereafter, pressure withina processing chamber, which has been kept under reduced pressure, isgradually increased up to atmospheric pressure. Or, preferably, dummypatterns of a sealing material (with a dot shape) are provided outsideof the patterns of the sealing material 12, and only the dummy patternsare cured with UV light. The pressure within the processing chamber,which has been kept under reduced pressure, is increased up toatmospheric pressure, and the patterns of the sealing material 12 arethen cured entirely.

Upon increasing the pressure to the atmospheric pressure from reducedpressure or upon attaching the pair of substrates, if pressure isapplied to the substrates, bending and cracking of the substrates can beprevented because of the columnar spacers 15 and the partition wall 16,thereby maintaining the constant gap between the substrates in theentire pixel portion.

Afterwards, the attached first and second substrates 10, 20 are dividedinto two panels by using a cutting device such as a scriber device, abreaker device, and a roll cutter (FIG. 1F). To prevent cutting defects,another columnar spacers may be provided outside of the sealing material12 prior to performing the dividing step. Thus, the two panels can befabricated from the pair of substrates. Thereafter, FPCs are pasted toeach of the panels by using a known method.

According to the above-mentioned steps, a light emitting device isachieved. The light emitting elements are sandwiched by the twosubstrates 10, 20 while maintaining a constant gap between thesubstrates, thereby preventing ingress of moisture into the lightemitting elements.

Alternatively, after forming the cathode 21 over the first substrate 10under reduced pressure, the first substrate can be attached to thesecond substrate 20 under reduced pressure without increasing thepressure within the processing chamber to the atmospheric pressure.Since the light emitting elements are sensitive to moisture, it iseffective that the step of forming the layer containing the organiccompound to the step of attaching the pair of substrates be carried outin an atmosphere with a dew point as low as possible.

FIG. 9A is a top view showing an example of the light emitting devicethus manufactured. Reference numerals 1201, 1203 denoted by chainedlines represent a source signal line driver circuit and a gate signalline driver circuit, respectively, whereas reference numeral 1202denoted by a dotted line represents a pixel portion. Reference numeral1207 denoted by a dotted line indicates a portion for connecting acathode or an anode of a light emitting element to a wiring of a lowerlayer. Reference numeral 1204 represents a sealing substrate; and 1205,a sealing material. The interior portion surrounded by the sealingmaterial 1205 is filled with a filler. Columnar spacers 1206 c areprovided in portions overlapping with the sealing material to improvethe adhesiveness between the pair of substrates and maintain a gaptherebetween. L-shaped spacers 1206 b are disposed outside of thesealing material to prevent cracking of the substrates upon dividing. Assubstitute for the L-shape spacers, another columnar spacers may beprovided outside of the sealing material to maintain the gap between thesubstrates, precisely. The columnar spacers 1206 a, 1206 d, and 1206 eare disposed in the interior portion surrounded by the sealing material1205 to maintain the gap therebetween.

Reference numeral 1208 indicates terminal portions connecting to wiringsfor transmitting signals input in the source signal line driver circuit1201 and the gate signal line driver circuit 1203. The terminal portions1208 receive video signals and clock signals from FPCs (flexible printedcircuits) 1209 that will be external connection terminals.

Embodiment Mode 2

A method for manufacturing a dual-emission type display device will bedescribed with reference to FIG. 5.

A base insulating film is formed on a substrate 400. In order to extractlight from the substrate 400 as a display screen, a substrate with alight transmitting property such as a glass substrate and a quartzsubstrate may be used as the substrate 400. A heat-resistant plasticsubstrate with a light transmitting property that can withstand aprocessing temperature can also be employed. A glass substrate is,herein, used as the substrate 400. The refractive index of the glasssubstrate is approximately 1.55.

As the base insulating film, a base film made from a silicon oxide film,a silicon nitride film, a silicon oxynitride film, and the like isformed. The base insulating film has light transmitting properties.Although the base insulating film has, herein, two-layer structure, itmay have a single layer or two or more layers of the above insulatingfilms. Note that the base insulating film is not particularly required.

A semiconductor layer is formed on the base insulating film. Thesemiconductor layer is formed as follows. A semiconductor film with anamorphous structure is formed by a known method (e.g., sputtering,LPCVD, and plasma CVD) and crystallized by a known crystallizationmethod (e.g., laser crystallization, thermal crystallization, andthermal crystallization using a catalyst such as nickel). A crystallinesemiconductor film thus obtained is patterned into a predetermined shapeby using a first resist mask that is formed with use of a firstphotomask. The thickness of the semiconductor film is set to be 25 to 80nm (preferably, 30 to 70 nm). A material for the crystallinesemiconductor film is not particularly limited, and silicon orsilicon-germanium (SiGe) alloy is preferably used.

A continuous wave laser may be used to crystallize the semiconductorfilm with the amorphous structure. When crystallizing the semiconductorfilm with the amorphous structure, in order to obtain large-size crystalgrains, it is preferable to use a continuous wave solid-state laser andsecond to fourth harmonics of fundamental waves. Typically, a secondharmonic (532 nm) or a third harmonic (355 nm) of an Nd:YVO₄ laser(fundamental wave with 1,064 nm) may be applied. In the case of using acontinuous wave laser, laser beam emitted from a continuous wave YVO₄laser with 10 W output power is converted in a harmonic by a nonlinearoptical element. Alternatively, a YVO₄ crystal and a nonlinear opticalelement may be put in a resonator so as to be converted into a harmonic.Preferably, laser beam having a rectangular shape or an elliptical shapeis formed on an irradiation surface by an optical system and irradiatedto an object to be processed. At this time, an energy density of about0.01 to 100 MW/cm² (preferably, 0.1 to 10 MW/cm²) is required. Thesemiconductor film may relatively be moved with respect to the laserbeam at a speed of about 10 to 2,000 cm/s and irradiated with it.

After removing the first resist mask, a gate insulating film coveringthe semiconductor layer is formed. The gate insulating film is formed byplasma CVD, sputtering, or thermal oxidation to have a thickness of 1 to200 nm. As the gate insulating film, an insulating film made from asilicon oxide film, a silicon nitride film, a silicon oxynitride film,and the like is formed. The gate insulating film also has the lighttransmitting property. When a thin gate insulating film is formed byplasma CVD, the thin film can be obtained with good controllability bylowering the deposition rate. For example, in the case where an RF poweris set to be 100 W, 10 kHz; pressure, 0.3 Torr; the flow rate of N₂Ogas, 400 sccm; and the flow rate of SiH₄ gas, 1 sccm, a silicon oxidefilm can be formed at a deposition rate of 6 nm/min.

A conductive film with a thickness of 100 to 600 nm is formed on thegate insulating film. For instance, the conductive film is, herein,formed by laminating a TaN film and a W film by sputtering. Although alamination layer of the TaN film and the W film is used here, thepresent embodiment mode is not particularly limited to the structure.The conductive film may be formed of an element selected from Ta, W, Ti,Mo, Al, and Cu, a single layer of an alloy material or a compoundmaterial containing the above elements as its principal constituent, ora lamination thereof. In addition, a semiconductor film typified by apolycrystalline silicon film that is doped with an impurity element suchas phosphorus may be used.

A second resist mask is next formed using a second photomask. Theconductive film is dry-etched or wet-etched by using the second resistmask to form gate electrodes for TFTs 402R, 402G, and 402B.

After removing the second resist mask, a third resist mask is newlyformed by using a third photomask. By using the resist mask, a firstdoping step for doping an impurity element that imparts n-typeconductivity (typically, phosphorus or As) to a semiconductor at lowconcentration is carried out so as to form an n-channel TFT (not shown).The resist mask covers a region to be a p-channel TFT and the vicinityof the conductive layer. In the first doping step, the semiconductorfilm is doped with the impurity element through the insulating film sothat a low concentration impurity region is formed. One light emittingelement is driven by using a plurality of TFTs. When one light emittingelement is driven by only p-channel TFTs, the above first doping step isnot required.

After removing the third resist mask, a fourth resist mask is newlyformed by using a fourth photomask. By using the resist mask, a seconddoping step is performed to dope an impurity element that imparts ap-type conductivity (typically, boron) to the semiconductor film at ahigh concentration so that a p-channel TFT is formed. In the seconddoping step, the semiconductor film is doped with the impurity elementthrough the gate insulating film so as to form a p-type highconcentration impurity region.

After removing the fourth resist mask, a fifth resist mask is newlyformed by using a fifth photomask. A third doping step is carried out todope an impurity element that imparts an n-type conductivity (typically,phosphorus or As) to the semiconductor film at a high concentration sothat an n-channel TFT (not shown) is formed. The resist mask covers aregion to be the p-channel TFT and the vicinity of the conductive layer.In the third doping step, the semiconductor film is doped with theimpurity element through the gate insulating film so as to form ann-type high concentration impurity region.

The fifth resist mask is removed. An insulating film containing hydrogenis formed. Thereafter, the impurity elements doped into thesemiconductor layer are activated and hydrogenated. As the insulatingfilm containing hydrogen, a silicon nitride oxide film (an SiNO film) isformed by PCVD. When the semiconductor film is crystallized by using ametal element promoting crystallization typified by nickel, getteringcan be performed to reduce the nickel in a channel formation region atthe same time of activating the impurity elements. The insulating filmcontaining hydrogen indicates a first layer of an interlayer insulatingfilm, and represents an insulating film containing silicon oxide with alight transmitting property.

Subsequently, a planarizing film, that will be a second layer of theinterlayer insulating film, is formed. The planarizing film is formed ofan inorganic material with the light transmitting property (such assilicon oxide, silicon nitride, and silicon oxynitride); aphotosensitive or nonphotosensitive organic material with the lighttransmitting property (such as polyimide, acrylic, polyamide, polyimideamide, resist, and benzocyclobutene); or a lamination thereof. Also, thefollowing films with the light transmitting properties can be used asthe planarizing film: an insulating film made from an SiOx filmcontaining alkyl group that is formed by application, e.g., aninsulating film formed using silica glass, alkyl siloxane polymer, alkylsilsesquioxane polymer, hydrogenated silsesquioxane polymer,hydrogenated alkyl silsesquioxane polymer, and the like. As examples ofsiloxane polymers, there are a coating material for an insulating filmsuch as #PSB-K1 and #PSB-K31 manufactured by Toray Industries, Inc. anda coating material for an insulating film such as #ZRS-5PH manufacturedby Catalysts & Chemicals Industries Co., Ltd.

A third layer with a light transmitting property of the interlayerinsulating film is formed. The third layer of the interlayer insulatingfilm is formed as an etching stopper film to protect the planarizingfilm, which is the second layer of the interlayer insulating film, uponpatterning transparent electrodes 403 in the subsequent step. When thetransparent electrodes 403 are patterned, if the second layer of theinterlayer insulating film can serve as an etching stopper film, thethird layer is not required.

By using a sixth resist mask, contact holes are formed in the interlayerinsulating film. The sixth resist mask is then removed, and a conductivefilm (TiN/Al/TiN) is formed. By using a seventh resist mask, theconductive film is etched (dry-etched using a mixed gas of BCl₃ and Cl₂)to form wirings (such as a source wiring and a drain wiring of the TFTs,and a power supply line). TiN is one of materials that are well-adheredto a planarizing film with a high heat resistant property. In order tomake good contact to a source or drain region of the TFTs, it ispreferable that the N content of TiN be set to be less than 44%.

By using an eighth resist mask, the transparent electrodes 403, i.e.,anodes of organic light emitting elements are formed with a thickness of10 to 800 nm. The transparent electrodes 403 can be, for example, madefrom a transparent conductive material with a high work function (4.0 eVor more) such as indium tin oxide containing an Si element (ITSO), andIZO (indium zinc oxide) formed by mixing indium oxide and zinc oxide(ZnO) of 2 to 20%, in addition to indium tin oxide (ITO).

By using a ninth resist mask, an insulator (also referred to as a bank,a partition wall, a barrier, a embankment, etc.) covering the edges ofthe transparent electrodes 403 is next formed. The insulator is formedof a photosensitive or nonphotosensitive organic material (e.g.,polyimide, acrylic, polyamide, polyimide amide, resist, orbenzocyclobutene) or an SOG film (e.g., a SiOx film containing alkylgroup) by application to have a thickness of 0.8 to 1.0 μm.

Layers 404, 405R, 405G, 405B, 406 containing organic compounds areformed by vapor deposition or application. To improve the reliability ofthe light emitting elements, degasification is preferably performed byvacuum heating prior to forming the layers 404 containing the organiccompound. For example, prior to vapor depositing an organic compoundmaterial, a heat treatment is desirably performed at 200 to 300° C.under a reduced pressure atmosphere or an inert atmosphere so as toeliminate gases contained in the substrate. When the interlayerinsulating film and the partition wall are formed of high heat resistantSiOx films, the heat treatment can be performed at a higher temperature(410° C.).

The first layers 404 containing the organic compound (first layers) areselectively formed on the transparent electrodes 403 using anevaporation mask by co-depositing molybdenum oxide (MoOx),4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPD), and rubrene.

In addition to the MoOx, materials with excellent hole injectingproperties such as copper phthalocyanine (CuPC), vanadium oxide (VOx),ruthenium oxide (RuOx), and tungsten oxide (WOx) can be used. Inaddition, a film formed by applying a polymer material with an excellenthole injecting property such as a solution containing poly(ethylenedioxythiophene) and poly(styrene sulfonate) (PEDOT/PSS) may be used asthe first layers 404 containing the organic compound.

Hole transporting layers (second layers) are next formed on the firstlayers 404 containing the organic compound by selectively vapordepositing α-NPD with use of an evaporation mask. In addition to theα-NPD, it is possible to use materials having the excellent holetransporting properties typified by aromatic amine-based compounds suchas: 4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation:TPD); 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviation:TDATA); and4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine(abbreviation: MTDATA).

Subsequently, light emitting layers 405R, 405G, and 405B (third layers)are selectively formed. To form a full color display device, evaporationmasks for respective luminescent colors (R, G, and B) are aligned tovapor deposit selectively.

As for the light emitting layer 405R emitting red light, materials suchas Alq₃:DCM, and Alq₃:rubrene:BisDCJTM are used. As for the lightemitting layer 405G emitting green light, materials such as Alq₃:DMQD(N,N′-dimethylquinacridone), and Alq₃:coumarin 6 are used. As for thelight emitting layer 405B emitting blue light, materials such as α-NPD,and tBu-DNA are used.

Electron transporting layers (fourth layers) are next formed on thelight emitting layers 405R, 405G, 405B by selectively vapor depositingAlq₃(tris(8-quinolinolate) aluminum using an evaporation mask. In placeof the above-mentioned material, it is possible to use materials havingsuperior electron transporting properties typified by metal complexeshaving quinoline skeleton or benzoquinoline skeleton such astris(5-methyl-8-quinolinolate) aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato) beryllium (abbreviation: BeBq₂), andbis(2-methyl-8-quinolinolate)-4-phenylphenolate-aluminum (abbreviation:BAlq), etc. Also, metal complexes having oxazole ligand or thiazoleligand such as bis[2-(2-hydroxyphenyl)-benzoxazolate]zinc (abbreviation:Zn(BOX)₂), and bis[2-(2-hydroxyphenyl)-benzothiazolate]zinc(abbreviation: Zn(BTZ)₂) can be used. In addition to the metalcomplexes, following materials can be used as the electron transportinglayers because of their excellent hole transporting properties:2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD); 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: OXD-7);3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ);3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ); bathophenanthroline (abbreviation: BPhen);bathocuproin (abbreviation: BCP); and the like.

Next, 4,4′-bis(5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs)and lithium (Li) are co-deposited to form an electron injecting layer(fifth layer) 406 on an entire of the substrate such that it covers theelectron transporting layers and the insulator. Damages that might becaused by sputtering for forming a transparent electrode 407 later canbe suppressed by using the benzoxazole derivative (BzOS). In addition toBzOs:Li, materials having excellent electron injecting properties suchas alkali metal compounds and alkali earth metal compounds, e.g., CaF₂,lithium fluoride (LiF), and cesium fluoride (CsF) can be used. Inaddition, a mixture of Alq₃ and magnesium (Mg) can be used.

The transparent electrode 407, that is a cathode of the organic lightemitting elements is formed on the fifth layer 406 to be 10 to 800 nmthick. Indium tin oxide including an Si element (ITSO), or indium zincoxide (IZO) in which zinc oxide (ZnO) of 2 to 20% is mixed into indiumoxide can be used for the transparent electrode 407 as well as indiumtin oxide (ITO).

The light emitting elements are thus achieved. The materials for theanode, the layers containing organic compounds (first to fifth layers)and the cathode, each of which are included in the light emittingelements, are selected arbitrarily. The thicknesses thereof are alsoadjusted arbitrarily. It is desirable that the anode and the cathode beformed of the same material and have almost same thickness, preferably,a thin thickness of about 100 nm.

If necessary, a transparent protective layer (not shown) for preventingingress of moisture is formed to cover the light emitting elements. Asilicon nitride film, a silicon oxide film, or a silicon oxynitride film(an SiNO film (N>O in composition ratio) or an SiON film (N<O incomposition ratio)), a thin carbon-based film (such as DLC film or a CNfilm), and the like, each of which can be obtained by sputtering or CVD,can be used.

A second substrate 408 is attached to the substrate 400 by using asealing material that contains a gap material for maintaining a gapbetween the substrates (e.g., a filler (fiber rod) and a fine particle(e.g., silica spacer)). The second substrate 408 may also be formed of alight-transmitting glass substrate or quartz substrate.

Structures 410 for maintaining the gap between the substrates are formedover the second substrate 408.

A drying agent may be provided in the gap between the pair of substrates(inert gas), or a transparent sealing material (e.g., an ultravioletcuring or thermal curing epoxy resin) may be filled therebetween. Byfilling the transparent sealing material (with a refraction index ofabout 1.50) between the substrates, the whole light transmittance can beimproved.

In the case of using a manufacturing device as shown in FIG. 6, afterforming the cathode, a sealing step can be carried out under reducedpressure without increasing the pressure up to atmospheric pressure.

FIG. 6 shows an example of the manufacturing device in which amultichamber for performing vapor deposition of an organic compoundlayer etc. is united with chambers for performing the sealing treatment.The multichamber united with the chambers for performing the sealingtreatment is intended to prevent ingress of impurities such as moistureand improve throughput.

In FIG. 6, the manufacturing device includes: gates 100 j, 100 n to 100w, 140 a to 140 f; an unloading chamber 119; transport chambers 108,114, and 147; delivery chambers 107, 111, and 141; film formationchambers 109, 110, 113, and 132; chambers 126R, 126B for installingevaporation sources; substrate stock chambers 130 a and 130 b; a curingchamber 143; an attaching chamber 144; a chamber 145 for forming asealing material; a pretreatment chamber 146; and a sealing substrateloading chamber 117.

A flow of performing the sealing step will briefly be explained below.

A first substrate, wherein a layer containing an organic compound, acathode, and the like are formed on an anode, is introduced in thetransport chamber 114, and stored in the substrate stock chambers 130 a,130 b or transported to the delivery chamber 141. Preferably, thetransport chamber 114, the substrate stock chambers 130 a, 130 b, andthe delivery chamber 141 are kept under reduced pressure.

The first substrate transported to the delivery chamber 141 is furthertransported to the attaching chamber 144 by a transporting unit 148 thatis installed in the transport chamber 147.

Columnar or wall-shaped structures have been provided on a secondsubstrate that serves as a sealing substrate, in advance. The secondsubstrate is introduced in the substrate loading chamber 117, and heatedtherein under reduced pressure so that degasification is performed. Thesecond substrate is then transported into the pretreatment chamber 146equipped with an UV irradiation mechanism by the transporting unit 148that is installed in the transport chamber 147. In the pretreatmentchamber, the surface of the second substrate is irradiated withultraviolet light. The second substrate is next transported to thechamber 145 for forming a sealing material so as to form a sealingmaterial thereon. The chamber 145 for forming a sealing material isequipped with a dispenser device or an ink-jet device. The chamber forforming a sealing material may also be provided with a baking mechanismor an UV irradiation mechanism to cure the sealing material temporarily.After curing the sealing material temporarily in the chamber 145 forforming a sealing material, a filler is dropped in a region surroundedby the sealing material.

The resultant second substrate is transported to the attaching chamber144 by the transporting unit 148, as well as the first substrate.

In the attaching chamber 144, after depressurizing the chamber, thefirst and second substrates are attached to each other. At this moment,the first and second substrates are attached to each other by moving anupper plate or a lower plate up and down. Upon attaching the twosubstrates under reduced pressure, the gap between the substrates iskept precisely because of the columnar or wall-shaped structures thathave been provided over the second substrate. The columnar orwall-shaped structures also serve to disperse pressure applied to thesubstrates so as to prevent breakage of the substrates.

Alternatively, the filler may be dropped in the region surrounded by thesealing material in the attaching chamber 144, instead of the chamber145 for forming a sealing material.

Instead of reducing the pressure within the entire processing chamber,after making a space between the plates an airtight space by moving theupper and lower plates longitudinally, the airtight space therebetweenmay be depressurized by a vacuum pump connected to a hole that isprovided in the lower plate. In such a way, the pressure within theairtight space can be reduced at short times since the volume to bedepressurized is smaller as compared with the case of depressurizing theentire processing chamber.

Further, a transparent window may be provided in one of the upper andlower plates such that the sealing material is cured by being irradiatedwith light that passes through the transparent window while maintainingthe gap between the upper and lower plates and attaching the substratesto each other. Or, dummy patterns of the sealing material are preferablyprovided outside of a pattern for the sealing material. After only thedummy patterns are cured with UV spot irradiation while maintaining thegap between the upper and lower plates and attaching the substrates toeach other, the pressure within the processing chamber that has beenkept under reduced pressure is increased up to atmospheric pressure. Theentire pattern of the sealing material is then cured under atmosphericpressure. When the transparent window is provided in one of the upperand lower plates, however, since a light shielding mask (that is a maskfor protecting light emitting elements from UV irradiation) etc. isformed in the subject substrates, it is difficult to position thesubject substrates such that the position of the pattern for the sealingmaterial is adjusted to a position of light that passes through thetransparent window. The positioning accuracy of the sealing materialwith respect to the light irradiation position is hardly ensured.Accordingly, it is more preferable that only the dummy patterns of thesealing material be cured by UV spot irradiation. Note that a pluralityof holes is formed in one of the upper and lower plates such that thedummy patterns are cured with UV light transmitting through theplurality of holes.

The pair of substrates, which is temporarily attached to each other, istransported to the curing chamber 143 by the transporting unit 148. Inthe curing chamber 143, the sealing material is completely cured bylight irradiation or heat treatment.

The pair of substrates is thus transported to the unloading chamber 119by the transporting unit 148. The pressure within the unloading chamber119, which has been kept under reduced pressure, is increased up toatmospheric pressure, and then the pair of attached substrates is takenout therefrom. As a consequence, the sealing step is completed whilemaintaining the constant gap between the substrates.

FIG. 7 is an overall view of the manufacturing device. In FIG. 7,identical portions to those in FIG. 6 are denoted by the same referencenumerals. The manufacturing device as shown in FIG. 7 includes:transport chambers 102, 104 a, 108, 114, and 118; delivery chambers 105,107, and 111; a preparing chamber 101; a first film formation chamber10611; a second film formation chamber 106B; a third film formationchamber 106G; a fourth film formation chamber 106R; a fifth filmformation chamber 106E; other film formation chambers 109, 110, 112,113, 131, and 132; chambers 126R, 126G, 126B, 126E, 126H for installingevaporation sources; pretreatment chambers 103 a and 103 b; a mask stockchamber 124; substrate stock chambers 130 a and 130 b; cassette chambers120 a and 120 b; and a tray installation stage 121. The transportchamber 104 a is provided with a transporting unit 104 b fortransporting a substrate 104 c, and the other transport chamberscomprise such transporting units, respectively.

By utilizing the manufacturing device as illustrated in FIGS. 6 and 7,subject substrates can be processed successively from the vapordeposition step to the sealing step. Note that since a higher vacuum isrequired in vapor deposition as compared with that in the sealing step,upon transporting the subject substrates to a chamber for the sealingstep from a chamber for vapor deposition, the vacuum is necessary to bereduced prior to performing the sealing step. In the sealing step, thevacuum is set to be 1 Pa or less such that sudden vaporization of asolvent, which is contained in the sealing material, is prevented. Toprevent adhesion of moisture etc., an inert gas (e.g., nitrogen gas)having a controlled dew point is preferably filled in the chambers(including the delivery chamber, the processing chamber, the transportchamber, the film formation chamber, etc.), other than the cassettechambers 120 a and 120 b; the transport chamber 118; the applicationchamber 112; a baking chamber 123; the tray installation stage 121; theunloading chamber 119; and the sealing substrate loading chamber 117.Preferably, pressure within such chambers is kept under reducedpressure.

As shown in FIG. 5, the transparent electrodes 403, 407 of the lightemitting elements are made from the light transmitting materials so thateach of the light emitting elements can emit light upward and downwarddenoted by arrows, i.e., through the both sides thereof.

Next, optical films (e.g., polarizing plates or circular polarizingplates) 401 and 409 are provided on the both sides of the first andsecond substrates to improve the contrast.

For instance, a λ/4 plate and a polarizing plate are sequentiallydisposed on the substrate 400 as the optical film 401, while a λ/4 plateand a polarizing plate are sequentially disposed on the second substrate408 as the optical film 409.

As for another example, a λ/4 plate, a λ/2 plate, and a polarizing plateare sequentially disposed on the substrate 400 as the optical film 401,while a λ/4 plate, a λ/2 plate, and a polarizing plate are sequentiallyformed on the second substrate 408 as the optical film 409.

In the present invention, light emitted from the light emitting elementsmay be either monochromatic light or full color light of R, G, and B.When using a luminescent material for white color, for example, a colorfilter or a color filter together with a color conversion layer may beused so as to achieve full color display or area color display. Or, whenusing a luminescent material for blue color, a color conversion layer isused to achieve the full color display or the area color display.

As set forth above, a polarizing plate, a circular polarizing plate, ora combination thereof can be provided in accordance with the structureof the dual-emission type display device. As a consequence, fine blackcolor can be displayed, thereby improving the contrast. In addition,reflected light can be prevented by forming a circular polarizing plate.

The present invention having the above-described structure will furtherbe described in detail in the embodiment below.

Embodiment 1

In the present embodiment, FIG. 8 shows an example of a manufacturingdevice that is partly different of those in FIGS. 6 and 7.

As well as FIG. 6 and FIG. 7, the manufacturing device as shown in FIG.8 includes: the transport chamber 108 for transporting a substrate tothe delivery chamber 111; the delivery chamber 107; the gates 100 j, and100 n to 100 s; and the film formation chambers 109, 110, 113, and 132.In the embodiment, the portions identical to those in FIG. 6 and FIG. 7will not be further explained for the sake of simplification. To preventmoisture from adhering, an inert gas (e.g., nitrogen gas) having acontrolled dew point is preferably filled in the chambers (including thedelivery chamber, the processing chamber, the transport chamber, a filmformation chamber, etc.), other than an unloading chamber 219 and asealing substrate loading chamber 217. Preferably, pressure in suchchambers filled with an inert gas is kept under reduced pressure.

In FIG. 8, reference numerals 200 t to 200 x, and 240 a to 240 eindicate gates, reference numerals 214, 243, and 248 indicate transportchambers, and a reference numeral 241 indicates a delivery chamber.

A flow of the sealing step will hereinafter be described briefly.

A first substrate in which a layer containing an organic compound, acathode, etc. have been formed on an anode is introduced in thetransport chamber 214 and transported to a sealing chamber 216.

Columnar or wall-shaped structures have been provided in advance over asecond substrate that serves as a sealing substrate. The secondsubstrate is introduced in the substrate loading chamber 217. The secondsubstrate is heated under reduced pressure to perform degasification.Thereafter, the second substrate is transported to an attaching chamber244 equipped with a mechanism for pasting a drying agent by atransporting robot that is installed in the transport chamber 248. Inthe attaching chamber 244, a drying agent that is attached on a tape ispeeled off from the tape and pasted to the second substrate. Theattaching chamber 244 further comprises a chamber 246 for providing adrying agent tape and a chamber 247 for gathering a tape that isseparated from a drying agent.

The second substrate is transported to a chamber 245 for forming asealing material via the transport chamber 248. In the chamber 245 forforming a sealing material, a pattern of a sealing material is formedover the second substrate. The chamber 245 for forming a sealingmaterial is equipped with a dispenser device or an ink-jet device. Thechamber 245 for forming a sealing material may further comprise a vacuumpump such that the pattern of the sealing material is formed underreduced pressure. A baking mechanism or an UV irradiation mechanism maybe provided in the chamber 245 for forming a sealing material to curethe sealing material temporarily.

The second substrate is next transported to the baking chamber 242 viathe transport chamber 243 so as to cure the sealing material formed overthe second substrate temporarily. The baking chamber 242 may comprises avacuum pump such that the sealing material is cured temporarily underreduced pressure. The second substrate on which the pattern of thesealing material is thus formed is transported to the sealing substratestock chamber 230 via the delivery chamber 241 and stored therein. Or,the second substrate is directly transported to the sealing chamber 216.

The second substrate that is stored in the sealing substrate stockchamber 230 is transported to the sealing chamber 216.

In the sealing chamber 216, the first substrate is attached to thesecond substrate under reduced pressure. The substrates are attached toeach other by moving an upper or lower plate longitudinally. Theattached substrates are transported to the unloading chamber 219 via thetransport chamber 214. The pressure within the unloading chamber 219 isgradually increased until it reaches the atmospheric pressure.Thereafter, the pair of attached substrates is taken out of themanufacturing device.

When the pair of attached substrates is exposed to outside air, a sealedspace surrounded by the sealing material and the pair of substrates iskept under reduced pressure. In addition, since the columnar orwall-shaped structures are formed over the second substrate, a constantgap can be maintained between the substrates while the sealed space iskept under reduced pressure, without bending the pair of substrates.

In the embodiment, the drying agent is disposed in the sealed spacesurrounded by the pair of substrates and the sealing material. In thiscase, when attaching the substrates to each other, the gap between thesubstrates is maintained by the columnar or wall-shaped structures thatare formed over the second substrate. The columnar or wall-shapedstructures also have an important role to disperse pressure applied tothe substrates so as to prevent cracking of the substrates. It ispreferable that the drying agent be disposed so as not to overlap thecolumnar or wall-shaped structures.

FIG. 9B is a top view of an example showing a light emitting device thusmanufactured. Reference numeral 1301 denoted by a chained linerepresents a source signal line driver circuit; 1303, a gate signal linedriver circuit; and 1302 denoted by a dotted line, a pixel portion.Reference numeral 1307 denoted by a dotted line indicates a connectionregion for connecting a cathode or an anode of a light emitting elementto a wiring for a lower layer. Reference numeral 1304 indicates asealing substrate; and 1305, a sealing material. An interior spacesurrounded by the sealing material 1305 is kept under reduced pressureand filled with an inert gas (typically, nitrogen gas). In thereduced-pressure space surrounded by the sealing material 1305, moistureis eliminated by the drying agent so that the inside of the space isdried completely. A grid-like spacer 1306 a is disposed in thereduced-pressure space surrounded by the sealing material 1305 tomaintain a gap between the substrates. A plurality of airtight spaces(4×4) is further provided by the grid-like spacer 1306 a within theairtight space surrounded by the sealing material 1305. A plurality ofwall-shaped spacers 1306 b disposed outside of the sealing materialprevents cracking of the substrates when the substrates are divided intomultiple patterns.

Reference numeral 1308 indicates a terminal portion connecting to awiring for transmitting signals input in the source signal line drivercircuit 1301 and the gate signal line driver circuit 1303, and receivesvideo signals and clock signals from an FPC (flexible printed circuit)1309, which will be an external input terminal.

The embodiment can be freely combined with Embodiment Mode 1 or 2.

Embodiment 2

Various kinds of electronic appliances can be manufactured by beingincorporated with a dual-emission type display device according to thepresent invention. Examples of the electronic appliances include: acamera such as a video camera and a digital camera; a goggle typedisplay (a head-mounted display); a navigation system; an audioreproduction device (such as a car audio and an audio component system);a personal computer; a game machine; a portable information terminal(such as a mobile computer, a cellular telephone, a portable gamemachine, and an electronic book); an image reproduction device providedwith a recording medium (typically, a device which can reproduce therecording medium such as a digital versatile disc (DVD) and displayimages thereof); and the like.

FIG. 10A shows an example of a folding cellular phone with adual-emission type display device (a double-sided display panel)according to the invention.

FIG. 10A is a perspective view showing the cellular phone that isopened, while FIG. 10B is a perspective view showing the cellular phonethat is folded up. The folding cellular phone includes: a main body2101; a housing 2102; display portions 2103 a, 2103 b; an audio inputunit 2104; an audio output unit 2105; operation keys 2106; an externalconnection port 2107; an antenna 2108; an image pickup unit 2109; andthe like.

The cellular phone as shown in FIGS. 10A and 10B includes the displayportions 2103 a and 2103 b that display high-definition full colorimages, respectively. One panel (i.e., a dual-emission type panel)includes the display portions 2103 a and 2103 b. By using thedual-emission type panel, an electronic appliance with plural displayscreens can be reduced in size, thereby reducing weight and the numberof component parts.

The dual-emission type display device as described in Embodiment Mode 1,Embodiment Mode 2, or Embodiment 1 can be used as the dual-emission typepanel. An optical film (such as a polarizing plate, a λ/4 plate, a λ/2plate) is properly disposed thereon.

The display portions 2103 a and 2103 b are identical in size and sharesame image signals. When an image is displayed on the display portion2103 a, the image is flipped horizontally on the display portion 2103 band the flipped image is displayed on the display portion 2103 b, aswell as the display portion 2103 a. Usually, the user watches onlyimages displayed on the display portion 2103 b when folding up thecellular phone, and only images displayed on the display portion 2103 awhen opening the cellular phone. Therefore, images may be switched byflipping the images horizontally in accordance with the state of thecellular phone such that the user can recognize the images.

The cellular phone as shown in FIGS. 10A and 10B can photograph a stillimage and a moving image by the image pickup unit 2109 (such as a CCD).Since the display portion 2103 b is provided in a side of the imagepickup unit 2109, a photographic subject can be displayed on the displayportion 2103 b. Therefore, when the user photographs he or her face byoneself, the user can release the shutter while checking the picture tobe photographed on the display portion 2103 b in real-time. Accordingly,the dual-emission type panel is convenient.

FIG. 10C is a perspective view of a personal laptop computer that isopened, while FIG. 10D is a perspective view of the personal laptopcomputer that is folded up. The personal laptop computer includes: amain body 2201; a housing 2202; display portions 2203 a, 2203 b; akeyboard 2204; an external connection port 2205; a pointing mouse 2206;and the like.

The personal laptop computer as shown in FIGS. 10C and 10D comprises thedisplay portion 2203 a displaying a high-definition full color imagewhen opening the computer, and the display portion 2203 b displaying ahigh-definition full color image when folding up the computer.Therefore, the user can conveniently recognize an image displayed on thedisplay portion 2203 b while carrying the folded laptop computer like anelectronic book.

FIG. 11A shows a large-size dual-emission type display device having alarge-size screen of 22 to 50 inches. The large-size dual-emission typedisplay includes: a housing 2701; a support base 2702; a display portion2703; a video input terminal 2705; and the like. Note that the displaydevice includes all display devices for displaying information such asone for a personal computer, one for receiving TV broadcasting, and onefor an interactive TV. According to the invention, a large-size, thin,lightweight display device with a large-size screen, that is capable ofpure black display and high-definition full color display, can beachieved.

FIG. 11B shows a wireless portable TV. A housing 2802 has a built-inbattery and a built-in signal receiver, and a display portion 2604 andspeaker units 2807 are driven by the built-in battery. The buttery canbe recharged repeatedly by a battery charger 2800. The battery charger2800 can transmit and receive an image signal, and transmit an imagesignal to the signal receiver of the housing. The housing 2802 iscontrolled by operation keys 2806. Since the housing 2802 can transmit asignal to the battery charger 2800 by operating the operation keys 2806,the device as shown in FIG. 11B can serve as a bi-directionalvideo-audio communication device. Further, by operating the operationkey 2806, a signal is transmitted to the battery charger 2800 from thehousing 2802, and the signal received by the battery charger is furthertransmitted to other electronic appliance so that communication controlof the other electronic appliance can be carried out. Accordingly, thedevice as shown in FIG. 11B can also serve as a general-purposeremote-control device. According to the invention, a relativelylarge-size wireless portable TV (22 to 50 inches) with a dual-emissiontype panel can be achieved.

FIG. 11C shows examples in which dual-emission type display devices aremounted on an exterior wall 2900 and a door 2906 of a shop or buildingsuch as a restaurant and a closing store. For example, when thedual-emission type display device is embedded in a frame 2902 of theexterior wall 2900 facing the street, like a window, both ones outsideand inside of the building can see information (e.g., advertisementinformation) displayed on a display portion 2903, simultaneously.Therefore, using the dual-emission type display device makes it possibleto serve as a store window for providing merchandise information to morepeople, namely, not only ones outside the shop but also ones inside theshop. The power consumption for only one panel is required even whendisplaying images on both display screens. In addition, advertisementinformation can be confirmed in a wide area around the display screens,and hence, the dual-emission type display device is useful.

Similarly, when a dual-emission type display device is mounted on thedoor 2906 as a display portion 2904, the display device can serve as ashow window. Because of using the dual-emission type display device,images displayed on the display portion can be seen in both cases wherethe door 2906 is closed and the door is fully opened, in which thedisplay portion 2904 is turned inside out. Reference numeral 2905represents a handle. When the dual-emission type display device isplaced a signboard, advertisement information can be seen and confirmedin a wide area around the display screens, and hence, it is useful.

The embodiment can be freely combined with Embodiment Mode 1, EmbodimentMode 2, or Embodiment 1.

According to the present invention, when two substrates are attached toeach other to encapsulate a light emitting element, pressure applied tothe substrates can be dispersed to prevent cracking of the substrates,thereby improving the yield.

What is claimed is:
 1. A light-emitting device comprising: a firstsubstrate; a pixel portion over the first substrate, the pixel portioncomprising a light-emitting element and a transistor; a second substrateover the pixel portion; a sealing material provided between the firstsubstrate and the second substrate with a closed pattern; and astructure comprising an organic material provided between the firstsubstrate and the second substrate, and provided on an outer side of aregion surrounded by the sealing material, wherein the sealing materialand the structure do not overlap each other.
 2. The light-emittingdevice according to claim 1, further comprising a second polarizingplate over the second substrate.
 3. The light-emitting device accordingto claim 1, wherein the light-emitting device is configured to emitlight from the light-emitting element through the second substrate. 4.The light-emitting device according to claim 1, wherein thelight-emitting element comprises a cathode, an anode, and a layercontaining an organic compound between the cathode and the anode.
 5. Thelight-emitting device according to claim 1, wherein the structure is oneof a columnar structure and a wall-shaped structure.
 6. Thelight-emitting device according to claim 1, wherein the structure is oneof a columnar spacer and a wall-shaped spacer.
 7. The light-emittingdevice according to claim 1, wherein an airtight space surrounded by thefirst substrate, the second substrate, and the sealing material is keptunder negative pressure.
 8. A light-emitting device comprising: a firstsubstrate; a pixel portion over the first substrate, the pixel portioncomprising a light-emitting element and a transistor; a second substrateover the pixel portion; a sealing material provided between the firstsubstrate and the second substrate with a closed pattern; a structurecomprising an organic material provided between the first substrate andthe second substrate, and provided on an outer side of a regionsurrounded by the sealing material; and an FPC, wherein the structure isprovided between the FPC and the pixel portion, and wherein the sealingmaterial and the structure do not overlap each other.
 9. Thelight-emitting device according to claim 8, further comprising a secondpolarizing plate over the second substrate.
 10. The light-emittingdevice according to claim 8, wherein the light-emitting device isconfigured to emit light from the light-emitting element through thesecond substrate.
 11. The light-emitting device according to claim 8,wherein the light-emitting element comprises a cathode, an anode, and alayer containing an organic compound between the cathode and the anode.12. The light-emitting device according to claim 8, wherein thestructure is one of a columnar structure and a wall-shaped structure.13. The light-emitting device according to claim 8, wherein thestructure is one of a columnar spacer and a wall-shaped spacer.
 14. Thelight-emitting device according to claim 8, wherein an airtight spacesurrounded by the first substrate, the second substrate, and the sealingmaterial is kept under negative pressure.
 15. The light-emitting deviceaccording to claim 1, further comprising a first polarizing plate overthe first substrate.
 16. The light-emitting device according to claim 1,wherein the structure further comprises a hygroscopic substance.
 17. Thelight-emitting device according to claim 8, further comprising a firstpolarizing plate over the first substrate.
 18. The light-emitting deviceaccording to claim 8, wherein the structure further comprises ahygroscopic substance.